The present invention relates to an integrated circuit device for RS-232C line receiver and, more particularly, to an integrated circuit device for RS-232C line receiver (hereinafter referred to as "RS-232 line receiver IC") conforming to the RS-232C standards for a digital data transmission system through an electric cable.
As a type of conventional line receiver IC conforming to the RS-232C standards, the line receiver IC shown in FIG. 3 is the most typical. In such conventional type RS-232C line receiver IC, the hysteresis width is determined by a feedback resistor and the input threshold is fixed. Therefore, although the characteristics of optimal input threshold for transmitting a high speed clock signal are different from those for transmitting a control signal, either of the characteristics must be sacrificed, which is a disadvantage as explained later.